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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/alpha/lib/strncpy.S
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/*

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 * arch/alpha/lib/strncpy.S

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 * Contributed by Richard Henderson ([email protected])

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 *

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 * Copy no more than COUNT bytes of the null-terminated string from

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 * SRC to DST.  If SRC does not cover all of COUNT, the balance is

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 * zeroed.

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 *

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 * Or, rather, if the kernel cared about that weird ANSI quirk.  This

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 * version has cropped that bit o' nastiness as well as assuming that

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 * __stxncpy is in range of a branch.

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 */

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	.set noat

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	.set noreorder

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	.text

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	.align 4

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	.globl strncpy

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	.ent strncpy

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strncpy:

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	.frame $30, 0, $26

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	.prologue 0

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	mov	$16, $0		# set return value now

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	beq	$18, $zerolen

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	unop

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	bsr	$23, __stxncpy	# do the work of the copy

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	unop

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	bne	$18, $multiword	# do we have full words left?

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	subq	$24, 1, $3	# nope

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	subq	$27, 1, $4

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	or	$3, $24, $3	# clear the bits between the last

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	or	$4, $27, $4	# written byte and the last byte in COUNT

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	andnot	$3, $4, $4

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	zap	$1, $4, $1

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	stq_u	$1, 0($16)

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	ret

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	.align	4

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$multiword:

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	subq	$27, 1, $2	# clear the final bits in the prev word

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	or	$2, $27, $2

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	zapnot	$1, $2, $1

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	subq	$18, 1, $18

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	stq_u	$1, 0($16)

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	addq	$16, 8, $16

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	unop

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	beq	$18, 1f

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	nop

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	unop

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	nop

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	blbc	$18, 0f

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	stq_u	$31, 0($16)	# zero one word

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	subq	$18, 1, $18

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	addq	$16, 8, $16

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	beq	$18, 1f

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0:	stq_u	$31, 0($16)	# zero two words

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	subq	$18, 2, $18

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	stq_u	$31, 8($16)

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	addq	$16, 16, $16

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	bne	$18, 0b

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1:	ldq_u	$1, 0($16)	# clear the leading bits in the final word

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	subq	$24, 1, $2

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	or	$2, $24, $2

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	zap	$1, $2, $1

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	stq_u	$1, 0($16)

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$zerolen:

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	ret

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	.end	strncpy

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